Monte Carlo Simulations of Copolymer Adsorption at Planar Chemically Patterned Surfaces: Effect of Interfacial Interaction

Abstract

Summary: Monte Carlo simulation utilizing the bond fluctuation model in conjunction with single and configurational biased Monte Carlo moves is used to study the adsorption of diblock (A-block-B) and alternating (A-alt-B) copolymers at flat, chemically heterogeneous surfaces comprising C and D domains. The main objective of this work is to address the effect of the strength of attraction between the adsorbing surface domains, D, and the copolymer adsorbing segments, B, on the copolymer's ability to recognize the chemical pattern on the surface. The results of our simulations reveal that both block and alternating copolymers have the ability to recognize the surface motif and transcribe it into the bulk material. The extent to which diblock copolymers transfer the chemical pattern from the surface to the bulk is relatively unaffected when the attractive B-D potential is increased beyond a certain critical value. This behavior stems from the brush-like conformation adopted by the diblock copolymer at the substrate. In contrast to the diblock copolymer, the adsorption of the alternating copolymer is influenced by the strength of the attraction between the copolymer's adsorbing segments and the adsorbing domains on the surface. Since the B segments are distributed evenly along the backbone, the alternating copolymers are more likely to adopt conformations in which the whole chain is “zipped” to the surface. The resultant entropic frustration is then alleviated through an increased formation of loops with little change to their length. Such conformational changes endow the alternating copolymer with the ability to invert the substrate pattern as the distance away from the surface is increased.